Integrated circuit (IC) devices typically include an IC chip housed in a package formed of plastic, ceramic or metal. The IC chip includes an integrated circuit formed on a thin piece (e.g., “chip”) of silicon. The package supports and protects the IC chip and provides electrical connections between the integrated circuit and an external circuit or system.
There are several package types, including ball grid arrays (BGAs), pin grid arrays (PGAs), plastic leaded chip carriers, and plastic quad flat packs. Each of the package types is typically available in numerous sizes and configurations. The package type and configuration selected by an IC manufacturer for a particular IC chip may be determined by the size and complexity of the IC chip and/or in accordance with a customer's requirements.
For example, BGA packages may include any suitable number of solder balls to provide electrical connections between the IC chip and an external circuit or system. The solder balls may be formed over all or a portion of a bottom surface of the package. For example, BGA packages that include solder balls formed over the entire package bottom are said to have a full footprint, while BGA packages that include solder balls formed around the periphery of the package bottom are said to have a peripheral footprint. In addition, the pitch, which may be defined as the lateral distance between the solder balls, may vary between BGA packages.
FIGS. 1A and 1B show bottom and side sectional views, respectively, of a typical BGA package 100 having a full footprint. BGA package 100 includes a plurality of solder balls 102 formed on a bottom surface 104a of a substrate 104. Balls 102 are arranged in a matrix spanning the length L and width W of substrate bottom surface 104a. An IC chip 106 is mounted on an upper surface 104b of package substrate 104. Bond wires 108 provide electrical connections between bonding pads 110 of IC chip 106 and contact pads 112 formed on substrate 104. Contact pads 112 are electrically connected to corresponding balls 102 by conductive vias 114 formed in substrate 104. A protective cover 116, such as a cap or “glob top”, is formed over IC chip 106 and bond wires 108.
FIGS. 2A and 2B show bottom and side sectional views, respectively, of a typical BGA package 200 having a peripheral footprint. Like BGA package 100 (FIGS. 1A and 1B), BGA package 200 includes a plurality of solder balls 202 formed on a bottom surface 204a of substrate 204 and connected to IC chip 206 by bond wires 208 and conductive vias 214. However, unlike BGA package 100, balls 202 of BGA package 200 are arranged around the periphery of substrate bottom surface 204a, thereby leaving a central area of substrate bottom surface 204a without balls 202.
IC manufacturers typically test their IC packages before shipping to customers using well-known IC testing systems. A typical IC testing system includes a device tester, a device handler, and an interface structure. The device tester includes a plurality of test probes that provide test signals to the interface structure, which in turn transmits signals between the device tester and the leads (e.g., solder balls) of an IC device under test (DUT). The device handler is a precise robot that automatically moves IC devices between a storage area and the interface structure.
FIG. 3 shows a top view of a conventional interface structure 300 that may be used to test BGA package 100 of FIGS. 1A and 1B. Interface structure 300 includes a rectangular-shaped printed circuit board (PCB) 302 having a socket 304 located in a central test area. PCB 302 is of a size and shape that allows it to be received into a docking area of an associated device tester (not shown). Socket 304 includes a plurality of compressible pins such as pogo pins 306 arranged in a matrix so as to mate with and contact corresponding balls 102 of BGA package 100 (not shown in FIG. 3). Thus, the arrangement of pogo pins 306 of socket 304 corresponds to the arrangement of balls 102 of BGA package 100. PCB 302 includes groups 308 of conductive contacts 310 positioned around the periphery of socket 304. Contacts 310 extend through a bottom surface of PCB 302 to receive corresponding test probes (not shown) extending from the device tester, and are connected to corresponding pogo pins 306 of socket 304 by conductive lines (e.g., metal traces) 312. For simplicity, only a few conductive traces 312 are shown in FIG. 3.
The arrangement of contact groups 308 shown in FIG. 3 is compatible with the Model TR-8 MDA tester from Checksum, Inc. of Arlington, Wash. For simplicity, each group 308 is shown to include 4 contacts 310, although groups 308 may include any suitable number of contacts 310. For example, for compatibility with the Model TR-8 MDA Tester, each group 308 includes 48 contacts 310.
FIG. 4 shows an exploded side view of a conventional IC testing system 350 employing interface structure 300 and a device tester 352 such as, for example, the Model TR-8 MDA tester. Computer 360, which may be, for example, a personal computer (PC), is connected to device tester 352 and includes well-known testing software residing in internal memory (e.g., system memory or a hard disk). BGA package 100 is mounted on socket 304 (for example, using a device handler) so that its solder balls 102 contact pogo pins 306 (not shown in FIG. 4) of socket 304. Interface structure 300 is mounted on docking area 356 of device tester 352 so that contacts 310 are aligned with and make electrical contact with corresponding test probes 354 of device tester 352. The testing software provides test and control signals to device tester 352 according to test parameters associated with BGA package 100. The test parameters may be stored in a file located in computer memory, or may be input into computer 360 using any suitable input device such as, for example, a keyboard (not shown).
Referring also to FIGS. 1A, 1B, and 3, device tester 352 provides the test signals through test probes 354 to contacts 310, along traces 312 to socket pogo pins 306, and finally to corresponding balls 102 of BGA package 100. For example, a test signal applied to contact 310a by a corresponding tester probe 354 of device tester 352 is routed along conductive trace 312a to pogo pin 306a, and thereafter to a corresponding ball 102 of BGA package 100. Signals are returned from BGA package 100 to device tester 352 in a similar manner.
A problem associated with conventional interface structure 300 is that socket 304 can support only one BGA package size and configuration (e.g., BGA package 100). Thus, if the physical dimensions of a package substrate do not match the size of socket 304, or if the number and placement of its solder balls do not match the arrangement of pogo pins 306, interface structure 300 cannot be used to test the package. For example, because BGA package 200 of FIGS. 2A and 2B has a peripheral footprint rather than a full footprint, and/or may have a different ball pitch than BGA package 100 of FIGS. 1A and 1B, interface structure 300 may not be suitable for testing BGA package 200. Accordingly, an IC manufacturer utilizing several BGA package sizes and configurations must purchase a separate interface structure for each BGA package size and configuration, thereby increasing device testing costs. In addition, switching between different interface structures mounted on a device tester undesirably increases testing time. Thus, there is a need for an interface structure that allows for testing BGA packages of different sizes and configurations.